This relates to graphics processing.
Shading is the process of applying lighting effects to an object to be depicted. Deferred shading is a popular way of rendering a scene where rendering is performed after the visibility (coverage) is resolved. Specifically shading is deferred until after all occlusions have been resolved. Typically this is done in two passes. The first pass writes out inputs required for shading (surface normals, depth, view vector etc.) into a buffer called a geometry or G-buffer. The second pass is a full screen pass (or a compute shader pass) where shading calculations are done.
For each G-buffer sample, shading is done by reading the G-buffer for the current sample, accumulating the contribution of all lights and then outputting the final surface color.
One advantage of deferred shading is that only visible surface fragments are shaded. Shading is deferred until all geometry processing is complete.
When visibility rates are different from the shading rate (e.g. as in multi-sampled anti-aliasing (MSAA) or Coarse Pixel Shading (CPS)), it is difficult to decide what rate the shading needs performed at (per pixel or per sample), because the G-buffer is available at the full visibility rate. Although it is safe, it is quite inefficient (and often not required) to shade the G-buffer at the visibility rate.